Chapter 23 Flashcards
what does safety involve?
safety googles, a laboratory coat or apron and closed-toed shoes
- Gloves are appropriate sometimes
what should all labs have
have an eyewash station, shower station, fire extinguisher, emergency exit
what is accuracy
a measurement giving the actual value for the sample with a limited deviation
what is precision
the repeatability of a set of measurements on the same sample
why is glass preferred for chemical application
bc of its strength, inertness, transparency, and heat resistance
what are Test tubes, beakers, and Erlenmeyer flasks
used for many of the routine mixing and reaction tasks of the lab
what are test tubes
are relatively small and allow a large number of samples to be arrayed in a task in a rack for easy processing
what are beakers
wide mouthed cylinders with a lip to allow pouring
-Flat bottom so they can stand on their own
what are Erlenmeyer flasks
tapered and therefore minimize accidental spills
- The neck of the flask allow sit to be clamped in place either on the laboratory bench or above it on a sand
- Some can be sealed with rubber, cork, or ground glass stoppers
- Flat bottom so they can stand on their own
what are round-bottom flasks
used for reaction, heating or vacuum applications
what does spherical shape and wall thickness of the round-bottom flask provide
-extra strength and fit into a heating mantle and the narrow neck allows the flask to be clamped into place
what kind of experiments round-bottom flasks used for
experiments that require that require distillation to isolate product
what is a retort for round-bottom flasks
a round vacuum flask with a long neck that extends to the side
- It is used for distillation and must be placed on a ring stand or heating mantle
what is a Extraction flask (separatory funnel)
a teardrop-shaped flask with a ground glass stopper at the top and a stopcock at the bottom
how are Extraction flask (separatory funnel) used
- 2 different solvents are mixed by shaking the flasks, venting to prevent breakage and are then allowed to separate by density, the lower layer is removed by draining through the stopcock
- often used to separate polar mc from non-polar mc, the 2 liquids in the separatory funnel must be immiscible to complete the separation
can a Extraction flask stand on its own
-placed in a ring stand bc cannot stand on its own
which pipets are made of glass and which are made of plastic
pastic: transfer pipet
glass: pasture pipet
small bottles
vials
cylindrical containers with wide openings that may be sealed
jars
used to contain vacuums
bell jars
shallow glass plates used as evaporating surfaces or to cover beakers
watch glass
___glassware is used for any lab measurement that requires accuracy and precision
calibrated
what is a graduated cylinder
a tall, narrow tube with volume markings increasing from bottom to top and a lip at the top for pouring
when do you see a concave meniscus
if the liquid is attracted to the side of the cylinder
when do you see a convex meniscus
mc of the liquid is more attracted to each other than the cylinder
what are burets and pipets used for
deliver exact volumes of liquids
what is a buret
a long tube that is clamped in place vertically with a stopcock at the bottom
- used to make solutions and to perform titrations
what is volumetric pipet
have a large bulb in the middle of the tube and deliver a single established volume of liquid with great accuracy and precision
what is graduated pipet
hand-held and controlled by a pipet bulb that maintains a slight vacuum at the top of the pipet
what is a volumetric flask
is used to make solutions that require a specific volume of liquid
what is a pH meter and how does it work
consists of a glass probe and an electronic meter
-measures the acidity or basicity of a solution by comparing the voltage ( electrical potential) produced by the solution compared to the voltage of a known standard solution and uses the difference in voltage ( the potential difference) between them to calculate the pH
what colour is litmus paper for acid, basic and neutral conditions
- red under acidic conditions ( <4.5)
- blue under basic conditions ( >8.3)
- purple neutral
what is calorimetry
a way for chemists to measure the energy content of a substance
how does a bomb calorimeter work
1) the fuel (sample being measured) is ignited, heating up the surrounding air
2) the air heats surrounding water and using the specific heat of the water it is possible to measure the heat content and thereby calculate the internal energy of the sample
